Abstract:

A new method is developed to effectively study the contributions of various coexisting conformations to the actual vibrational spectrum of liquid polyethylene oxide (PEO). By defining six conformations for the-(CH₂CH₂O)-unit, four isomers from the combinations of all the same EO conformations [(TGT)₁₀, (TTT)₁₀, (TTG)₁₀, and (GTG)₁₀] and three isomers from the combinations of other EO conformations were constructed. Their optimized geometric structures and the corresponding vibrational frequencies were then computed. The unified standards that describe the different types of the CH₂ scissor and CH₂ twist vibrational modes for PEO400 are proposed through the analysis of the normal modes. The relationships between the four CH₂CH₂-OCH₂CH₂ conformations and the various CH₂ scissor and CH₂ twist vibrational modes and frequencies are determined, and the results are used to assign the practical vibrational spectra.

Key words: Polyethylene oxide, Conformation, Raman spectrum, Density functional theory calculation